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Openbuilds Cam not loading DXF files properly

Discussion in 'CAM' started by Metalguru, Jul 9, 2019.

  1. Metalguru

    Metalguru Master
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    I was playing around trying to get OB Cam to load a DXF file of the Ox gantry plates. Some of the radius's on corners and slots seem to be reversed, ie instead of a corner radius spanning 90 degrees, it spans 270 degrees see screen shot below:

    upload_2019-7-9_20-18-29.png

    File loads fine in Estlcam. What's going on here?

    MG
     

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  2. Ariel Yahni

    Ariel Yahni OpenBuilds Team
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    Sometimes the DXF parser seems to not like open paths, your had many so I just joined all of the. Give it a try
     

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  3. Metalguru

    Metalguru Master
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    It does load, but I don't see why. I went back and looked at the original file under a microscope (extreme zoom) on my CAD program, and I could see no discontinuities whatsoever in the file. How did you see them? Also, the drawing works fine with my go-to CAM program, ESTLCAM, it loads and I can define the toolpaths with no problems at all.

    MG
     
  4. Ariel Yahni

    Ariel Yahni OpenBuilds Team
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    I just opened in 2 different apps ( illustrator and Rhino ) and clicked the outside perimeter but in only selected a section.

    Maybe @Peter Van Der Walt can chime in and let us know the technical term im missing
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The original file contains objects of type ARC.
    Our parser only supports Polylines (as a Polyline is a guaranteed "vector") - so use the Explode command to convert any spline/arc and any other non-polyline entities to Polylines. A little prep work helps the math work better.

    (as you know what you want to cut, you can be the best judge of which loose segments and entities to join together into a polyline for the "shape" to make sense)
     
  6. Metalguru

    Metalguru Master
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    #6 Metalguru, Jul 10, 2019
    Last edited: Jul 10, 2019
  7. Award

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    Not all dxf files are the same. If you open up your original dxf file and then Ariel Yahni's dxf file side by side in a text editor you can see the difference in just the first few lines of text in the header. This is a good example of why the dxf extension without a version sub script is misleading as CAD programs don't necessarily implement the same standard even if we are ultimately trying to describe the same physical object for our CNC machines.

    The dxf parser that Open Builds CAM uses is able to handle a subset (R14) of the Autocad 2012 specification: https://images.autodesk.com/adsk/files/autocad_2012_pdf_dxf-reference_enu.pdf

    The original source code for the dxf parser is here on github: gdsestimating/dxf-parser

    Although it looks like Peter has modified it recently to implement support for splines:
    OpenBuilds/OpenBuilds-CAM

    EstlCAM isn't open source and there doesn't seem to be much information about which dxf versions it supports. It is difficult to see how it approaches parsing a dxf file and what version it supports as opposed to the Open Builds CAM approach.

    This doesn't answer your question but even a cursory glance at the links I have provided shows why parsing the dxf format is such a nightmare.

    Cheers

    Adam
     
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  8. Metalguru

    Metalguru Master
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    That's all very well and good, but don't you think that this is important enough information to let people know Before they try to use the product instead of as an afterthought when they complain about it?
     
  9. Award

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    As I don't work for Open Builds I don't think I can comment on what their policy should be regarding their free, open source software.

    However I note that it is described as a beta and not a full release candidate. I personally wouldn't complain about a free product that allows me access to the source code to modify as I see fit which I view as a great model especially as I haven't spent my money developing, maintaining or updating it but maybe I'm just weird! The free open source model vs the proprietary code and pay model argument and their various shortcomings are probably not going to be resolved here.
     
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  10. Alex Chambers

    Alex Chambers Openbuilds Team
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    DXF files have been problematic throughout their history - including sometimes from one Autodesk product to another.
    Alex.
     
  11. Christian James

    Christian James Veteran
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    Yep, that's why I never go near them.
     
  12. Metalguru

    Metalguru Master
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    I do have a problem with software that doesn't work, doesn't work as expected, or is buggy as hell. And I can comment on what policy should be, as can anyone else. That is exactly how things improve and become better products, by listening to what users have to say about it, and acting on the feedback.

    I also don't have any time for developers, free or not, who don't do proper documentation for their products. That, in my opinion, is just plain lazy. The documentation should be done before the software is released, beta or no beta. I was an Industrial Designer for 35 years, and I can safely say that no product I designed ever was released without documentation. In fact, in some cases, I wrote the documentation first and designed the product around it.

    Software developers saying "well, you are not doing it right" don't have a leg to stand on when there is no documentation to say which way is right. If the software works, but only on certain cases of input, with no documentation on what cases work and what don't, it can't hit the recycle bin fast enough. My time is valuable, and the less of it I have to spend head scratching about someone else's problems, the better.

    And, I can complain all I want about software that doesn't work as advertised, free or not free, open source or code and pay. Since I'm not a programmer, I care not about the open source aspect. I'm not going to be fixing any bugs or adding code to this any time soon. I just want a product that works.

    There are lots of other free software fish in the sea when it comes to CAM programs, so I'll just stick with the ones that I know will do the job for me. I may come back in a couple of years to see if they fix any of this.

    MG
     
    #12 Metalguru, Jul 11, 2019
    Last edited: Jul 11, 2019
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    SVGs tend to be easier to parse, but harder to maintain scale :)
    No format is perfect sadly, but one quickly learns the tricks of the trade.
    Its not unique to the open source world either - try sending some DXFs to a contract factory to professionally produce a few parts, and you'll inevitably end up with a back-and-forth emailing about the format. And no... its not just DXFs, even something meant to super universal like STEP files can land you in trouble, even when the manufacturer is state-of-the-art. Its just how the industry goes.

    DXFs work good as long as you stick to older revisions (yeah for OB CAM but also for my local signshop's laser cutting service, and the sheetmetal processing plant I used to use a lot before joining OB)
    R12 is like the universal standard for "works with just about anything"

    More important, just because its drawings in a DXF doesnt make it a "manufacturable" drawing.
    Polylines as the entity type makes CNC software's hearts sing... as a polyline is object that not only tells you what you drew, it automatically has all segments nicely connected, and even maintains the direction of the path. Thats what polylines were invented for. Refusing to use them, well, thats gonna only get the negative nancies sooo far before they'll have to cave in :)
     
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  14. Award

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    I'm not sure why you are having a temper tantrum with me as I have nothing to do with Open Builds. I was trying to answer what I thought was a genuine question not realising that you already knew the answer and just wanted to have a rant.

    Having a look at your website: 3D Tech Works – Custom Benchtop CNC Machines and Supplies it looks like you supply Open Builds products and your own designs so why don't you just contact them directly rather than airing your dirty laundry in the forum? You are just wasting my valuable time and frankly alienating a genuine paying Open Builds customer.
     
  15. Alex Chambers

    Alex Chambers Openbuilds Team
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    Gentlemen - can you please both cool things down - both posts are rather off putting to other forum members. If you wish to continue this discussion please do so in a private conversation.
    Thank you, Alex.
     
  16. Metalguru

    Metalguru Master
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    What temper tantrum? All I did was refute your statements and state my own opinion on the topic at hand. I simply stated facts. Last time I checked, that is what forums are for. I have no beef with you. There was nothing in my post directed at you at all. I have done nothing or said nothing to "alienate" anyone.

    Contact who directly? Openbuilds? This is an Openbuilds forum, and that's exactly what I just did.

    As I said, I am not by any stretch of the imagination a programmer. Thus pointing a bunch of programmer links at me has no effect at all. I don't care about programming, all I asked for was proper documentation pointing out the fact that I should be using R12, or R14, or whatever, rather than forcing me to waste time trying to load files that don't work, and then having to waste more time to ask why.

    MG
     

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